The file "cleanAir0109" contains information on enforcement of the Clean Air Act (CAA) in the fifty U.S. states from 2001-2009. Descriptions the variables, with sources in parenthesis, are as follows:

* state: A numeric index of each state, ordered alphabetically.

* year: Calendar year of an observation.

* stateact: The number of CAA enforcement actions taken by state's environmental agency in a given year. (Source: http://www.epa-echo.gov/echo/idea_download.html)

* federalact: The number of CAA enforcement actions taken by the U.S. Environmental Protection Agency in a state in a given year. (Source: http://www.epa-echo.gov/echo/idea_download.html)

* total: The total number of CAA enforcement actions taken either by federal or state authorities. (Source: http://www.epa-echo.gov/echo/idea_download.html)

* unemployment: The unemployment rate in a state in a year. (Source: http://data.bls.gov/)

* manufacturing: Manufacturing outputs by state and year in chained 2000 dollars. (Source: http://www.bea.gov/regional/gsp/)  

* demgov: Indicator equal to 1 if governor is a Democrat, 0 otherwise. (Source: Klarner 2003 and http://www.indstate.edu/polisci/klarnerpolitics.htm)

* demlegis: The proportion of state legislators who are Democrats. (Source: Klarner 2003 and http://www.indstate.edu/polisci/klarnerpolitics.htm)

* ne: Indicator equal to 1 if the state is Nebraska, 0 otherwise. (This allows the analyst to model-out the state with a nonpartisan legislature.)

* lagstate: A state's CAA enforcement actions in the previous year.

* lagfed: The EPA's CAA enforcement actions in a state in the previous year.

* grants: The dollar amount of federal non-construction grant allotments to a state from the EPA for clean air purposes. (Source: http://yosemite.epa.gov/oarm/igms_egf.nsf/HomePage?ReadForm)

* groups: The number of clean air-related lawsuits by environmental groups originating in a state in a given year. (Source: Bureau of National Affairs. 2001-2010. "Environment Reporter--Cases." Vol. 51-70. Washington, DC: The Bureau of National Affairs, Inc.)

* demunified: Indicator equal to 1 if the Democratic party controls the governorship and the legislature, 0 otherwise. (Source: Klarner 2003 and http://www.indstate.edu/polisci/klarnerpolitics.htm)

* repunified: Indicator equal to 1 if the Republican party controls the governorship and the legislature, 0 otherwise. (Source: Klarner 2003 and http://www.indstate.edu/polisci/klarnerpolitics.htm)

* legcont: The proportion of chambers controlled by the democratic party. (Source: Klarner 2003 and http://www.indstate.edu/polisci/klarnerpolitics.htm)

* abbr: Two-letter postal abbreviation of the state's name.

